This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Study Aims are: 1) To conduct an observational study to characterize the incidence and management of hypotension in infants who are mechanically-ventilated at 72 hours postnatal age, 34 weeks gestation and to define a target population for an RCT of hydrocortisone for the treatment of hypotension in such infants. 2) To determine the incidence of hypotension in this population 3) To describe the diagnoses and characteristics of infants with hypotension 4) To characterize the therapies given for hypotension in this population, including volume expanders, vasopressors/inotropes and glucocorticoids (timing of introduction, type, reason, duration and amount). Note that the term, vasopressor/inotrope will be used to describe dopamine, dobutamine, epinephrine, phenylephrine, norepinephrine or other vasopressor/inotrope/catecholamine. 5) To determine baseline vasopressor/inotrope exposure in this population for the purposes of sample size calculations and comparisons for the proposed RCT. 6) To characterize short term outcomes for this cohort of mechanically ventilated term and late preterm infants, including ventilation days, days on oxygen, days of age at time of full enteral nipple feedings, length of hospital stay, and mortality, and to analyze the association of these outcomes with hypotension as defined above and the receipt of vasopressor/inotrope therapy. 7) To finalize the design and conduct a randomized, masked, placebo-control multi-center clinical trial, to determine whether hydrocortisone therapy improves cardiovascular instability and reverses shock, using the primary outcome measure of exposure to vasopressors/inotropes AND affects other short term outcomes, including ventilation days, days on oxygen, days to full nipple feedings, length of hospital stay, and mortality.